With development of wireless communications, update of wireless networks in many areas has already started, and it is already attempted that a conventional 2G (2nd Generation) network is replaced with a 3G (3rd Generation) network or a 4G (4rd Generation) network. However, in many areas, because the 2G network is relatively mature and comprehensive, the 2G network will still be used in a relatively long period of time, which causes a phenomenon that the 2G network and the 3G/4G network coexist. The 2G network is generally in a GSM standard, the 3G network is generally in a UMTS standard, and the 4G network is generally in an LTE standard.
Currently, GSM, UMTS, and LTE networks coexist in a networking manner, and the networking refers to that a macro cell and a micro cell form a network, where the macro cell and the micro cell may be in a same network standard, or may be in different network standards. In this case, user equipment needs to have an access stratum (AS) and a non-access stratum (NAS) that support multiple network standards, and an access stratum in each network standard is in a one-to-one correspondence with only a non-access stratum in the network standard.
An inventor of the present invention finds in a long-term research and development that, for user equipment supporting multiple network standards, the user equipment communicates with a core network by using an access network, and because a mapping relationship between an access stratum and a non-access stratum in the user equipment is fixed, when the user equipment switches a network standard, not only the user equipment needs to switch the access stratum that performs a signaling interaction with the access network, but also an interface between the access network and the core network needs to be switched. In this way, a non-access stratum message sent by the core network can be processed by the non-access stratum, which corresponds to a network standard of the non-access stratum message, of the user equipment. Therefore, when the prior-art user equipment accesses a network in which multiple network standards coexist, a signaling interaction is complex, a delay is relatively long, and it is not flexible enough.